Here, we argue that this metric has some fundamental issues and support this with empirical observations.
Firstly, dance is not strictly about matching local minima in joint speed to beats.
Instead, the beats of the music are a loose guide for timing, rhythm, and transitions between movements and dance steps.
Secondly, while encouraging an overall alignment with the beat of the music is intuitive, the metric as presented in Li et al. [1]} implies that high-quality dances that contain motions with local minima between beats should be penalized, and the metric as presented in Siyao et al. [2]} implies that dances that skip over beats should receive corresponding penalties. While each of these metrics holds some truth, neither is strictly correct: a perfectly valid dance which aligns with the music in double time or half time will be scored very poorly by at least one of the two metrics.
